1. Field of the Invention
This invention pertains to methods and apparatus for generating heat from particulate-laden gas or directly from waste fuels such as wood waste.
2. Description of the Prior Art
Wood waste fuel burners, commonly known as hog fuel burners, have generally been extremely inefficient in combustion, discharging undesirable amounts of gaseous and particulate pollution. In addition, when these burners are coupled to a boiler the gases emitted to the boiler for heating are dirty causing depositions on the heat transfer tubes of the boiler which require frequent and expensive cleaning. Frequently, the particulate matter in the exhaust gases is also highly abrasive to the boiler heat transfer elements. As a result, conventional practice is to build an extremely large furnace chamber for a boiler allowing the discharge gases from the burner to reach a very low velocity so that particulate matter in the exhaust can drop out of the gas stream. Also, because of retained particulate matter, the gas passages in the tube banks of conventional boilers are generally made wider to minimize passage obstruction. Gas velocities of 50 to 60 ft./sec. are common in hog or wastewood fuel boilers while velocities of 110 to 120 ft./sec. are the rule in oil and gas fired packaged or field erected boilers. And lastly, once through the boiler, the economizer and the air preheater, the exhaust gases in conventional hog fuel boilers have to be cleaned in multiple cyclones (multicones) followed, typically, by electrostatic precipitators. What the industry has long needed is a clean burning waste fuel burner which can deliver exhaust gases as clean as those produced by oil and gas burners. The same burner could also replace oil and gas burners on lime kilns, plywood veneer dryers, particle board dryers, lumber dry kilns, etc.